Speaker enclosure



United States Patent 3,142,353 SPEAKER ENCLOSURE Carmine V. Todiseo, 100Augusta Drive, North Syracuse 12, NY. Filed Oct. 25, 1962, Ser. No.232,955 4 Claims. (Cl. 181-31) This invention relates to a loud speakerenclosure assembly for sound reproduction purposes. It is a primaryobject of the present invention to provide a speaker enclosure incombination with a single electro dynamically driven speaker capable ofreproducing sound within the entire audible range of frequenciesincluding the lower bass frequencies.

Another object of the present invention is to provide a speakerenclosure for a single speaker, the enclosure being of the bass reflextype yet approaching an enclosure of a loaded horn by utilizing a gangof exponential horns replacing the ports normally associated with a bassreflex enclosure, the volume of the enclosure also being reduced belowthat of a bass reflex sound chamber designed in accordance with thepiston area and characteristic of the single speaker and the lowestfrequency it is capable of reproducing.

The important discovery of the present invention, is the fact that aplurality of exponential horns that are geometrically similar andreduced in scale with respect to a single equivalent horn, may reproducesound with the same tone or quality as the single equivalent horndesigned for a particular speaker enclosure to obtain optimum soundreproduction and hence in accordance with the type, ratings anddimensions of the single speaker with which the plurality of horns areassociated and the rearwardly loading sound chamber. As a resultthereof, a tremendous reduction in the size of the enclosure is effectedcompared to the size that would be necessary to support a full sizedrear loaded exponential horn. The foregoing division and addition ofsound is also accomplished without any sacrifice in acousticalefliciency.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

FIGURE 1 is a perspective view of one form of speaker enclosure inaccordance with the principles of the present invention.

FIGURE 2 is a side sectional view of the speaker enclosure taken througha plane indicated by section line 2-2 in FIGURE 1.

FIGURE 3 is another form of speaker enclosure constructed in accordancewith the principles of the present invention.

FIGURE 4 is a sectional view taken substantially through a planeindicated by section line 44 in FIG- URE 3.

FIGURE 5 is a third form of a speaker enclosure constructed inaccordance with the principles of the present invention.

FIGURE 6 is a sectional view taken substantially through a planeindicated by section line 6-6 in FIG- URE 5.

Referring now to the drawings in detail, it will be observed fromFIGURES 1 and 2, that a speaker enclosure assembly generally referred toby reference numeral 10 includes an outer cabinet made of any suitablematerial such as plywood, including a top 12, a bottom 14, side 16 and aclosed back panel 18. A partition member 20 is mounted within theenclosure more closely spaced to the rear panel 18 than the open frontwhich is generally referred to by reference numeral 22. A centrallylocated rectangular opening is formed in the partition member 20 towhich a speaker box 24 is connected, the box 24 being opened rearwardlythereof and having an opening 26 in a front panel 28, in which there issupported a speaker generally referred to by reference numeral 30. Thespeaker 30 is of the electro dynamic type and capable of handling theaudible range of frequencies. As illustrated in FIG- URE 2, the speaker30 includes a rearwardly tapering cone 32 from which the sound energy isradiated, the cone being driven by the power driven component 34 mountedrearwardly thereon. The cone 32 is rear loaded so that the higherfrequencies of sound energy while directly radiated in a forwarddirection at a relatively high energy level as indicated by the arrows36 will not so emerge from the rear chamber. The lower frequencies ofsound energy on the other hand, will be radiated in a rearward directionas indicated by the arrows 38 for reinforcement purposes.

The rearwardly directed lower frequency energy, radiated from thespeaker cone 32, will therefore enter the reflex sound chamber includingthe chamber 40 formed rearwardly of the partition member 20.Accordingly, the sound chamber 40 is lined with a sound absorbingmaterial 42 such as felt padding whereby only the lower frequency soundwill be propagated in a forward direction through a plurality of ports44 formed in the partition member 24). In this sense, the sound chamber40 constitutes a bass reflex enclosure. In this regard, a rear loadingbass reflex chamber when exposed to atmospheric pressure through forwardradiating outlet ports, must enclose a predetermined mass of air toattain transmission of the desired low frequency sound energy with arelatively low compression of the air. However, the volume of thechamber 40 is substantially less than the limit prescribed for such bassreflex sound chamber in accordance with the present invention. Instead,the volume of the sound chamber 40 is reduced in favor of an increase inpressure in the chamber allowed to expand through a horn passage outlet.The chamber volurne is therefore selected in accordance with differentcriteria involving the throat area of a full sized exponential horn or asingle equivalent horn designed in accordance with the size of thespeaker, the mass of its piston and magnet, the flux density thereof,and resonant frequency of the speaker and the desired lowest or cut-offfrequency capable of being reproduced. However, instead of using thesingle equivalent rear loaded horn for which the volume of the soundchamber 40 is designed, a plurality of geometrically similar exponentialhorns 46 are utilized to thereby significantly reduce the size of theenclosure that would otherwise be necessary to support and mount asingle full sized horn or one designed in accordance with theaforementioned criteria. The throat end 48 of each of the horns isaccordingly fitted within the ports 44 in the partition member 20, theports 44 and the horns being spaced with respect to each other so as toaccommodate the enlarged mouth ends 50 of the horns. The number of horns46 selected will be such that the total length of all of the horns willequal the length of the referred to single equivalent horn, the totalthroat areas of all of the horns will equal the throat area of thesingle equivalent horn and the total mouth areas of the horns will equalthe mouth area of the single horn. Accordingly, each of the horns 46,will be of equal reduced scale with respect to the single equivalenthorn, the scale or dimensional reduction ratio being equal to the numberof horns found to be most efficient in connection with the type ofspeaker being utilized. It has been found, that the scale most efficientfor a 12-inch diameter speaker is between 32 and 38. It should howeverbe appreciated that the optimum scale for other size speakers willdiffer and that the dimensional restrictions referred to are mere- 1yexemplary. In this manner, it has been found that the rearwardlyreflected sound energy at the lower frequencies, is conducted throughthe horns 46 in a forward direction emerging in phase with the directradiation from the speaker 30 and adding up to the lower frequencycharacteristics of the sound energy originating from the speaker.

It will be observed, from FIGURE 1, that the horns 46 are arranged in apattern about the centrally disposed speaker box 24. It will beappreciated however, that other arrangements of the plurality of hornswith respect to the single speaker, may be adopted such as illustratedin FIGURES 3 and 4. The speaker enclosure assembly 52 illustrated inFIGURES 3 and 4 therefore includes two groups of exponential horns 54and 56 disposed on either side of the speaker box 58 and disposed at aslight rearward angle thereto in order to increase the range of thespeaker. In FIGURES 5 and 6, two speaker boxes 60 and 62 are arranged onopposite sides of a. plurality of horns 64 including a number sufficientto accommodate each of the speaker boxes in accordance with theprinciples of the invention as described with respect to FIG- URES 1 and2. Accordingly, as more clearly seen in FIGURE 6, the speaker enclosureassembly generally referred to by reference numeral 66 includes apartition member 68 which separates the enclosure into two soundchambers 7 0 and 72 respectively associated with a group of horns 64 andone of the speaker boxes with speaker mounted therein. The speakerenclosure assembly 66 is thereby rendered ideally suited for stereoreproduction.

From the foregoing description, it will be apparent that the speakerenclosure may be constructed in accordance with the principles of thepresent invention capable of reproducing the sound of a true full sizerhorn and within a physical space substantially smaller than thatordinarily associated with such a full sized horn.. Also, the speakerenclosure is capable of operating at a higher efficiency because ofbetter loading of the speaker and the utilization of both front and rearradiated acoustical power. The enclosure assembly also facilitates thedispersion of the sound and constitutes a better coupling of the highpressure acoustical power produced by the speaker with the low pressureof the atmosphere.

It will also be observed, that despite the reduced size of theenclosure, there is little, if any, sacrifice of horn size because ofphysical restrictions, to thereby effect a true reproduction of the lowbass frequency depending on the cut off frequency for which the singleexponential horn is designed which is equivalent to the plurality ofhorns actually utilized. Also, all of the horns are mounted on straightaxes so as to avoid the frictional acoustical losses characteristic offolded horn arrangements.

Utilizing the constructional principles for the speaker enclosure ashereinbefore described, it has been discovered that a plurality of hornsmay faithfully reproduce the attributes of a true full scaledexponential born when certain conditions are met. These conditions,include the use of a plurality of horns which are geometrically similarto the single equivalent horn, having length and passage areas, the sumsof which are equal to the corresponding length and passage area of thesingle equivalent horn. Also, the volume of the sound chamber must be inproportion to the determined area of the throat of the full sizedequivalent horn for equivalent rear loading thereof for reproducing thelower bass frequencies of the sound energy radiated from the speaker.Accordingly, the dimensions of the full scale equivalent exponentialhorn will be designed in accordance with the size of the speaker, themass of its piston, its magnet weight, its gauss rating, its resonentfrequency and the desired lowest cut off frequency. Finally, it has beendiscovered that as a result of the foregoing constructional principlesin connection with the design of a speaker enclosure, the lowerfrequency energy components can be divided, phased and passed throughthe horns and allowed to expand at a pre-determined mathematical rate soas to emerge at the same low pressure side of the speaker enclosure,recombining to produce the original low frequency as originally radiatedby the speaker.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly, all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention asdesired.

What is claimed as new is as follows:

1. A sound reproducing device comprising, power driven means, soundradiating means mounting said power driven means and responsive toenergization thereof for effecting direct radiation of sound energy in aforward direction, reflex chamber means mounted rearwardly of saidradiating means for conducting rearwardly directed sound energy fromsaid sound radiating means, said chamber means having a volumesubstantially equal to the volume occupied by a mass of air that wouldbe displaced by the radiating means for propagation of sound energythrough a single equivalent rear loaded exponential horn having acertain length, throat and mouth areas designed for optimum soundreproduction with said reflex chamber means, and a plurality ofdimensionally reduced exponential horns forming outlet passages fromsaid chamber means forwardly directing said sound energy conductedthrough said chamber means, said plurality of horns being geometricallysimilar to said single equivalent horn and having lengths, throat andmouth areas the sums of which respectively equal said certain length,throat and mouth areas of the single equivalent horn.

2. In combination with a speaker radiating sound energy forwardly andrearwardly therefrom, an acoustical enclosure comprising, a front panelmounting said speaker for directly radiating sound energy forwardlytherefrom, side walls extending rearwardly from the front panel beyondthe speaker, a partition member mounted between said side wallsrearwardly of the speaker forming an opening aligned with the speakerthrough which sound energy is adapted to be radiated rearwardly forpropagation through an equivalent full-sized exponential horn havingcertain dimensions designed to reinforce bass frequencies of the soundenergy radiated from the speaker, a back panel connected to said sidewalls for enclosing a sound chamber rearwardly of the speaker defining avolume designed for said propagation of the sound energy radiatedrearwardly from the speaker, and a plurality of smaller exponentialhorns extending forwardly from the partition member to the front panelfor forwardly conducting sound energy radiated rearwardly from thespeaker through the sound chamber, each of said smaller horns havingdimensions reduced from said certain dimensions of the fullsized horn inproportion to the number of said plurality of smaller horns.

3. The combination of claim 1, wherein said plurality ofhhorns aremounted in adjacent parallel relation to each 0t er.

4. The combination of claim 1, wherein the number of said plurality ofhorns is between 32 and 38 for use when associated with a soundradiating cone of 12-inch diameter.

References Cited in the file of this patent UNITED STATES PATENTS1,869,178 Thuras July 26, 1932 2,971,598 Sieler Feb. 14, 1961 3,047,090Pruden July 31, 1962 FOREIGN PATENTS 384,973 Great Britain Mar. 6, 1931484,704 Great Britain May 9, 1938

1. A SOUND REPRODUCING DEVICE COMPRISING, POWER DRIVEN MEANS, SOUNDRADIATING MEANS MOUNTING SAID POWER DRIVEN MEANS AND RESPONSIVE TOENERGIZATION THEREOF FOR EFFECTING DIRECT RADIATION OF SOUND ENERGY IN AFORWARD DIRECTION, REFLEX CHAMBER MEANS MOUNTED REARWARDLY OF SAIDRADIATING MEANS FOR CONDUCTING REARWARDLY DIRECTED SOUND ENERGY FROMSAID SOUND RADIATING MEANS, SAID CHAMBER MEANS HAVING A VOLUMESUBSTANTIALLY EQUAL TO THE VOLUME OCCUPIED BY A MASS OF AIR THAT WOULDBE DISPLACED BY THE RADIATING MEANS FOR PROPAGATION OF SOUND ENERGYTHROUGH A SINGLE EQUIVALENT REAR LOADED EXPONENTIAL HORN HAVING ACERTAIN LENGTH, THROAT AND MOUTH AREAS DESIGNED FOR OPTIMUM SOUNDREPRODUCTION WITH SAID REFLEX CHAMBER MEANS, AND A PLURALITY OFDIMENSIONALLY REDUCED EXPONEN-